Failure probability analysis and design comparison of multi-layered SiC-based fuel cladding in PWRs

A modified Weibull failure probability model that considers the impact of compressive stress on cladding failure probability is deduced in detail, and then it is used to calculate the failure probability of different multi-layered SiC-based cladding designs under the reference high burnup PWR conditions. The result shows that two-layer cladding with inner SiCf/SiC composite and outer CVD-SiC monolith design has the lowest failure probability. Further analysis indicates that neglecting compressive stress impact on failure probability calculation will bring relatively large failure probability departure when the cladding internal pressure is relatively low. Parameter sensitivity analysis that evaluates the effect of each parameter +/- 10% variation from the reference value on failure probability shows that increasing the Weibull parameters and eta value (the ratio of the compressive to tensile strength of the material) can both reduce cladding failure probability. In addition, it also shows that failure probability is the most sensitive to the change of Weibull modulus. In order to reduce cladding failure probability and improve the accuracy of failure probability prediction, it is necessary to improve the value of these parameters and make the measured values as accurate as possible. At last, several methods are recommended to reduce cladding failure probability in terms of the improvement of SiC-based material structure and property and optimization of fuel cladding structure.